The game in which you show your testicles and or penis to an unexpecting person who is in the same room. If they are caught looking, you get to kick them in the ass while ridiculing them about how much of a faggot they are.
Methods known to have been used are:
1) The Brain: squishing your testicles together so that they look like a brain.
2) The Goat: tucking your penis and testicles between your legs while mooning the person.
3) The Wristwatch: Wrapping your cock and balls around your wrist.
4) The Bat Wing: Sheltering you're penis while stretching your sack just enough so that it looks like a bat wing.

Among others

Prankster: You know the smartest organ in the body is?
Unexpecting person: What?
Prankster: THE BRAIN!! *shows cock*
UP: *looks unexpectredly* AAHHHHHHHHHHHHH!!
Prankster: HA FAGGOT!! *kicks UP in the ass.*
And that's how you play the Fag Game!